Screw jack



July 2l, 1931. J. w. BATE SCREW JACK Filed Jan. 3. 1927 2 SheetsTSheet 1 Patented July 21, 1931 UNITED STATES PATENT OFFICE I JOHN lW. IBATE, F RACINE, WISCONSIN, .ASSIGNOB '.l'O- WALKER IANUFACTURING COM- lIEANY, OF RACINE, WISCONSIN, A. CORPORATION 0F WISCONSIN SCREW TACK application inea January e, 1927. serial no. isaeeo.

This invention relates to screw jacks particularly-to double lift screw jacks which are used on automobiles Ahavin balloon tires. The invention is fully descr1bed in the following speciication and shown in the accompanying drawings, in which:

Flgure 1 is a vertical section showing the jack 1n lowered position;

Fig. 2 is a horizontal section on the line l 13 2 2 of Fig. 1;

Fig. 3 is a view similar to Fig. 1 showing the jack in raised position;

Fig. 4 is a part1al sectional view on Athe line 4-4 of Fig. 3,;

Fig. 5 is a similar view on theline 5--5 of Fig. 3; and

Fig. 6 is a developed View of the plate on the line 6-6 of Fig. 5.

The embodiment illustrated comprises a .20 hollow housing 10 having a ledge in its upper portion on which rests a ball thrust bear- 1ng 11 which carries a nut 12 on the outer end of which is formed a bevel gear 12a. vThis gear is driven by means of a bevel pinion 13 which is inned to a shaft 14, the latter being journaled) in suitable bearings in the housing 10. This shaft is provided with a squared outer end 14a to receive a suitable crank for turning the same. The nut 12 is provided with an annular groove 12" into which projects the inner end of a retaining screw 12. The nut 12 is internally threaded to receive the threaded outer screw 15, the threads of this screw stopping short of the bottom. This screw in turnv is hollow and threaded at its upper portion'15a to receive the threaded inner screw 16, the threads of which raise or stop short of the bottom of the screw. The inner screw is assembled by inserting through the bottom of the outer screw 15, and has a cap 17 which is secured thereon by means of a pin 18. When the outer screw is inserted full depth as shownv in Fig. 1, it is prevented from entering further vby any suitable means such as an indentation 15b on the outer s crew i 15 which strikes the nut 12.

A tubular element 19 surrounds the outer screw 15 .and has an year 419l which is bent inwardly so as to engage the groove 15 in the outer screw 15 as shown in Figs. 3 and 4.

.The pin 22 is provided with a head and carries a spring 24 which normally vpresses the late 2O into contact with the cover plate 23.

he cover plate 23 is provided with an ear 28a which fits into a suitable projection in the bottom of the housing so as to prevent this cover plate from turning.. The cover plate is also provided with two tup-struck ears 23 which are adapted to register with openings 20a in the plate 20.

The operation of the jack is as follows: Starting with the 'ack parts in the position shown in Fig. 1, a er the shaft 14 is turned in a direction to lower the jack, the movement will be resisted by the inner screw with the cap 17 when it is 1n contact with a load which thus prevents it from turning. If,- however, there is no load on the jack, the inner and outer screws will be turned with the nut 12 and the outer' screw acting through the ear 19 will cause the plate 20 to turn in a clockwise direction as shown in Fig. 5. As it does so the openings 20a will ratchet over the ears 23".

When the shaft 14 is turned in a direction to raise the outer screw, the ears 23b strike the edges of the openings 20'aL thereby preventing the element 19 and the outer screw 15 from turning. The nut 12 therefore feeds the outer screw upwardly regardless whether or not the inner screw 16 turns with the outer screw, as when no load is applied, or whether it is prevented from turning as when a load is applied to the cap 17. Thus, as the nut 12 is turned the outer screw is raised with the turning until the ear 19s on the element 19 reaches the lower end of the key-way 15. When this happens the element 19 is raised lifting the plate 20 against the action of the spring 24 until the plate 20 clears the top of the ears 23". As soon as this happens the 100 zov . screw 15 to turn with the nut 12.;

v when the outer screw turns with the nut 12,

the inner screw is fed through the nut 15 at the upper end of the outer screw. If the nut- 12 is turned in a direction to raise the load,'the inner screw will continue to raise until (he unthreaded end of the screw strikes the nut 15.

The lowering operation is the reverse of that used for raising. As the nut 12 and outer screw are turned, the inner-screw 16 will be fed in until the cap 17 encounters the upper end of the outer screw 15 which will cause the outer screw to be held thereby forcing it to turn in the nut 12. If now the nut continues to turn in a direction to lower` the jack, the outer screw member vwill be lowered until it is stopped at the bottom by the burred thread 15b as has been previously described.

While I have shown and described but a single embodiment of this invention, it is to be understood that it is capable of many modiications. Changes therefore in the construction and arrangement may be made which do not depart from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. In a jack, a housing, inner and outer telescoping screw liftin members, a nut carried by said housing or lifting the outer screw, means for rotating said nut, an element adapted to engage said outer screw to prevent its rotation except at the top of its vertical movement, said element being connected to said housing to prevent the element from turning in one direction but permitting it to turn in the other direction, and means for disconnecting said element from said housing when the outer screw member is raised a, predetermined amount to permit the outersscrew member to turn with the nut. y

2. In a jack, a housing, inner and outer telescoping screw liftin members, a nut carried-by said housing For liftingthe outer screw, means for rotating said nut, a key-way in the outer screw, an element having an ear engaging said key-way, means normally holding said element in contact with said housing, interengageable means permitting said element to be turned in one direction but preventing it fromv turning in the :other direction, the ear on said element striking the ower end of the key way as said outer screr Carried by said housing for lifting the outer is raised to the top of its movement to li t said element out of engagement with said interengaging means to permit said element to turn with the nut in either direction.

3. In a jack, a housing, inner and outer engagement with said ratchet teeth to permit said element to turn with the nut in either direction.

4. In a jack, a housing, 'inner and outer telescoping screw lifting members, a nut carried by said housing for lifting the outer screw, means for rotating said nut, a keyway in the outer screw, an element having an ear engaging said key-way, means yieldably holding said element in contact with said housing, ratchet teeth on said housing and element permitting said element to be turned in one direction but preventing it from turning in the other direction, the ear on said element striking the lower end of the keyway as said outer screw is raised to the top of its travel.

5. In a jack, a housing, inner and outer telescoping screw lifting members, a nut car-` ried by said housing for lifting the outer screw, means for rotating said nut, means for preventing rotary movement in one direction of said outer screw during the middle portion of its vertical movement but permitting rotary movement only in one direction 'at the bottom of said vertical movement, said means including a plate rotatable about an axis substantially coincident with the axis of said screws, and interengaging parts on said plate and housing.

6. In a device of the character set forth, al

housing, a rotatable interiorly threaded nut carried by said housing and adapted to serve as a driving member, an exteriorly and interiorly threaded outer screw meshing within said nut, an inner screw member meshing within the threads of said outer screw, cooperating meansron the housing and o. ter screw normally serving to prevent rotary movement in one direction of the outer screw, means cooperating with and actuated by said outer screw for disengaging said cooperating means, and means or rotating said nut. i

' 7 In a jack, a housing, inner and outer telescoping screw lifting members, a nut screw, means for rotating said nut, cooperating means' on said housing and outer screw serving to prevent the outer screw from rotating in one direction, but permitting.. the rotation of said outer screw in the other direction, andV means for disconnecting said co-operating means to permit rotation of said outer screw.

8. In a jack, a housing, inner and outer vtelescoping screw liftin members, a nut carried by said housing or lifting the outer screw, means for rotating said nut, cooperating means on said housing and outer screw serving to prevent the outer screw from rotating in one direction, but permitting the rotation of said outer screw in the other direction, and means for disconnecting said co-operating means to permit rotation of said outer screw when at the upper limit of its travel.

9. A lifting jack comprising a housing, an interiorly threaded driving member carried by, said housing, inner Aand outer telescoping screw lifting members, said outer screw member meshing within said driving member, cooperating means carried by Sai housing and outer screw member serving to prevent rotation of said outer screw in one direction when at the lower limit of its travel., thereby causing said outer screw to rise, and means cooperating with and actuated by said outer screw for disengaging said cooperating means to permit rotation of said outer screw. f

In testimony whereof I have hereunto set my hand this 24th day of December, 1926.

JOI-IN W. BATE. 

